Table 3.

Number of insomnia symptoms and incidence rate ratio of ED visits and hospitalizations: results from multivariable negative binomial regression models*

	Health services use unweighted mean ± SE	Model I† IRR¶ (95% CI#) n = 4,239	Model II‡ IRR (95% CI) n = 4,191	Model III§ IRR (95% CI) n = 4,095	Model IV|| IRR (95% CI) n = 4,048
Emergency department visit
0 Insomnia symptoms	0.46 ± 0.02	Reference	Reference	Reference	Reference
1 insomnia symptom	0.61 ± 0.04	1.35 (1.13, 1.60)**	1.17 (0.98, 1.40)	1.28 (1.07, 1.53)**	1.16 (0.96, 1.40)
2 insomnia symptoms	0.95 ± 0.07	2.15 (1.79, 2.58)***	1.72 (1.41, 2.09)***	1.70 (1.40, 2.07)***	1.52 (1.23, 1.87)***
All-cause hospitalizations
0 Insomnia symptoms	0.25 ± 0.01	Reference	Reference	Reference	Reference
1 insomnia symptom	0.31 ± 0.02	1.25 (1.01, 1.53)*	1.09 (0.88, 1.35)	1.16 (0.95, 1.41)	1.15 (0.97, 1.36)
2 insomnia symptoms	0.55 ± 0.06	2.27 (1.73, 2.97)***	1.69 (1.29, 2.22)***	1.65 (1.28, 2.13)***	1.21 (1.02, 1.44)*

* NHATS 2011; N = 4,289; community-dwelling older adults continuously enrolled in Medicare FFS for 365 days or who died within 365 days from the interview date. Responses of “every night” or “most nights” were categorized to indicate the presence of insomnia symptoms.

^†Model I adjusted for demographic characteristics (age, sex, race/ethnicity, education).

^‡Model II adjusted for Model I covariates + mental health characteristics (depressive and anxiety symptoms).

^§Model III adjusted for Model I covariates + physical health characteristics (BMI, number of medical conditions).

^||Model IV fully adjusted for demographic, mental health, and physical health characteristics.

^¶IRR = incident rate ratio.

^#CI = confidence interval.

*p < 0.05, **p < 0.01, ***p < 0.001.